To add a photo to your signature, edit your signature to include a link to the image, like this:
[img]http://example.photo.host.com/mypictures/selectedpicture.jpg[/img]

Please include only a small picture in your signature; keep the file size under 8k, and use an image no more than about 200px high and no more than about 400px wide. Use a resolution of 72dpi. Also, give some thought to the content of the image. It's best to try to keep them relevant to this board. A photo of your car(s), car part(s), or yourself, for example.